Heads-up displays (or “HUDs”) have been in use at least since the 1960s, predominantly in military vehicle applications. HUDs of that nature generally create a read-out of vehicle and navigation-related information on or near a semi-transparent canopy and within in a pilot's natural line of site for observing the environment surrounding the vehicle that he or she is controlling. Often, such HUDs operate by reflecting light off of semi-transparent surfaces and into the pilot's field of vision by an information read-out projector.
Structural stabilizing devices have also been used in conjunction with camera systems for years, and include rolling dollies and the steady-cam, developed by Garrett Brown. Such stabilizing devices create a smooth-follow effect when recording visual information with a camera that is moving over uneven terrain or while in the hands of a vertically oscillating operator—e.g., a person walking—by the use of iso-elastic spring-loaded arms.